1. Field of the Invention
The present invention relates to embroidery machine, and more particularly, to an embroidery machine, in which a presser foot (a cloth pressing member) can be separately driven by its own drive source, independently from the drive source of a needle bar.
2. Description of the Related Art
Generally, an embroidery machine is a biaxial positioning control machine in which an embroidery stitch frame for fixing fabric undergoes horizontal motion in x-axis and y-axis directions while a needle bar thereof moves up and down.
Since this embroidery machine does needlework while the embroidery stitch frame, fixing the fabric, is transferred in x-axis and y-axis directions, the precise and constant-speed movement of the embroidery frame has a close relationship to the quality of an embroidered pattern.
Accordingly, a drive source of the embroidery machine, which transfers the needle bar in vertical directions and the embroidery stitch frame in the x-axis and y-axis directions, is generally implemented with a servo motor, which can be precisely controlled, or a motor, the position of which can be controlled.
FIG. 1 is a perspective view illustrating of the embroidery machine and partially expanded view of sewing head, FIG. 2A is a perspective view illustrating a drive structure for a presser foot and a needle bar of the embroidery machine of the prior art, and FIG. 2B is an expanded view of part “A” of FIG. 2A.
As shown in FIG. 1, a plurality of sewing heads 2 is fixedly arranged in the front portion of an upper beam of an embroidery machine 1 along the length thereof. In each of the sewing heads 2, an upper shaft (not shown) is arranged to laterally extend through a sewing arm 3, and a needle bar support case 4 is assembled to the front portion of the sewing arm 3 in such a fashion that the needle bar support case 4 is laterally movable.
In the lower portion of the needle bar support case 4, a plurality of presser feet 5 (so-called cloth pressing members), which act to prevent a sheet of cloth to be sewn from coming loose when it is being sewn, is provided. Each of the presser feet 5 is set to be vertically movable in cooperation with a needle bar (see the reference number 18 in FIG. 2A).
The needle bar 18 is set to be vertically movable using the rotation driving force of an upper shaft motor (not shown), and a needle (not shown), which forms sewing eyes in the sheet of cloth to be sewn, is mounted on the lower end of the needle bar 18.
Now the drive structure for the presser foot 5 and the needle bar 18 will be described more fully with reference to FIGS. 2A and 2B. A needle bar driving cam 10 is attached to the outer circumference of an upper shaft, which rotates using the rotation driving force of the upper shaft motor.
A needle bar driving rod 11 is mounted on the outer periphery of the needle bar driving cam 10 in such a fashion that the needle bar driving rod 11 is vertically displaceable in response to the amount of eccentricity of the needle bar driving cam 10.
The needle bar driving rod 11 is connected to an intermediate portion of a needle bar drive lever 12. Accordingly, the needle bar drive lever 12 can vertically pivot around a predetermined rotation point by a predetermined amount corresponding to the amount of eccentricity of the needle bar driving cam 10.
The needle bar drive lever 12 is connected, by a needle bar link (not shown), to a needle bar drive block 13, which is vertically movable on a needle bar guide shaft 15, so that the needle bar drive block 13 can vertically move to the extent that the needle bar drive lever 12 rotates.
A needle bar controlling block 14, which is rotatably provided inside the needle bar drive block 13, can be coupled to or decoupled from a needle bar holder 17a, which is fastened to the outer circumference of the needle bar 18. A presser foot holder 6 is mounted on the outer circumference of the needle bar 18 under the needle bar holder 17a, in such a fashion that it can move vertically.
A spring 19 having a predetermined elastic force is mounted between the needle bar holder 17a and the presser foot holder 6, and cooperates with the needle driver 18 in order to drive the presser foot 5.
The presser foot holder 6 is fixedly fastened with the presser foot 5, which prevents the sheet of cloth to be sewn from coming loose while it is being sewn. Now the drive structure for the needle bar 18 and the presser foot 5, as constructed above, will be described in more detail.
The driving force of the upper shaft rotates the motor upper shaft, which in turn rotates the needle bar driving cam 10 fastened to the upper shaft, so that the needle bar driving rod 11, the needle bar drive lever 12 and the needle bar drive block 13 operate cooperatively.
In a position where the needle bar holder 17a, which is fixedly fastened to the outer circumference of the needle bar 18, and the needle bar controlling block 14, which is inserted into the needle bar drive block 13, are coupled with each other, the needle bar 18 vertically reciprocates in response to the vertical movement of the needle bar drive block 13. Here, the presser foot holder 6, fastened to the presser foot 5, operates using the elastic force of the spring 19.
That is, the needle bar holder 17a, which moves downward, generates a pressing force on the spring 19, thereby pressing down the presser foot holder 6. Then, the presser foot 5, fastened to the presser foot holder 6, moves downward in cooperation with the needle bar 18.
Conversely, when the needle bar holder 17a moves upward, the pressing force on the spring 19 is released, so that the needle bar holder 17a on the lower end of the needle bar 18 pulls the presser foot 5 upward, thereby moving the presser foot 5 upward.
The conventional drive structure for the presser foot 5, as described above, does not have a driving source, but operates in cooperation with the movement of the needle bar 18. Accordingly, there are problems in that an operator or a user cannot freely change some parameters of the presser foot 5, such as the stroke (i.e., the distance between the top dead point and the bottom dead point), the bottom dead point, and the moving track.
During the downward movement of the presser foot 5, the presser foot holder 6 contacts the outer surface of the needle bar support case 4 to stop the presser foot 5. However, the contact between the needle bar support case 4 and the presser foot holder 6 produces noise upon impact. Furthermore, since contact is frequent, the presser foot holder 6 is constantly vulnerable to damage.